This invention relates to a portable working machine provided with a centrifugal air blower which is designed to be driven by means of a prime mover such as an air-cooled two-stroke internal combustion engine. More specifically, this invention relates for example to a shoulder type chemicals spraying machine for performing a spraying work of chemicals, or to a shoulder type air-blowing cleaner for collecting scattered objects such as fallen leaves and dusts by making use of air to be ejected from an air blower.
The conventional portable working machine of this kind such as a shoulder type chemicals spraying machine for instance is constructed generally as seen in Japanese Utility Model Publication H5-19549. Namely, it comprises a centrifugal air blower which is mounted in an upright state on a shouldering frame having an L-shaped configuration as viewed laterally and attached with a shouldering strap, and a prime mover such as an air-cooled two-stroke internal combustion engine which is mounted on the rear side of the air blower (on the rear portion of the shouldering frame) for driving the air blower.
Further, a separate chemicals storage tank is connected via a flow rate adjusting device to an upper portion of a volute case of the air blower. The chemical in the chemicals storage tank is made to be sucked into the volute case through the flow rate adjusting device, and then, while being carried by the flowing air, ejected from an air-ejecting nozzle which is projected downward diagonally from one side (usually right side) of the volute case, the ejected chemicals being ultimately ejected into the outside atmosphere after passing through a bent pipe, a bellows type flexible pipe and a blowing pipe.
However, the aforementioned conventional portable working machine provided with a centrifugal air blower is accompanied with the following problems.
Namely, since the air inlet port of the air blower is generally formed on a back of the shouldering frame, a relatively large air intake gap for introducing air from the outside atmosphere is inevitably formed between the shouldering frame and the air blower (the volute case of the air blower). As a result, the heavy weight portions such as the air blower, the chemicals storage tank and the prime mover are displaced rearward from the back of the shouldering frame by a distance corresponding to the air intake gap. In this case, as the center of gravity of the heavy weight portions such as the air blower, the chemicals storage tank and the prime mover is located further away from the back of the shouldering frame, the working machine constituted by these heavy weight portions is more likely to be moved away from the back of the shouldering frame, so that it becomes more difficult to easily carry the working machine on an operator's back, thus deteriorating the operability and portability of the working machine.
In the case of the conventional working machine, the shouldering frame, the volute case, the chemicals storage tank, the flow rate adjusting device, etc. are generally individually manufactured in advance, and subsequently, integrally assembled. Therefore, the conventional working machine is accompanied with the problems that it requires a large number of parts, it is heavy and bulky as a whole, it is difficult to assemble, and that the manufacturing cost of the working machine is relatively high.